1. Field of the Invention
The present invention relates to a disc cartridge having a shutter for closing and opening a head insertion hole of the disc cartridge.
2. Description of the Related Art
A conventional disc cartridge having a floppy magnetic disc in the thin cartridge case is shown in FIG. 1, wherein the cartridge comprises a thin case 51 of a generally rectangular shape and made of hard synthetic resin material, a magnetic disc 52 rotatably enclosed in the case 51 and a shutter 53 to be slidably mounted on the case 51 so as to move along one side or front side of the case 51.
In the central portion of the case 51, there are defined a circular opening 54 and a head accessing opening 55. A shallow recess 56 is defined on the top wall of the case 51 in the region near the head accessing opening 55 for sliding the shutter 53 pass the head accessing opening 55. A guide slot 57 is also defined in the top wall along the front side of the case 51 for guiding the movement of the shutter 53.
Conventionally the shutter 53 is formed of a stainless steel plate formed in a generally U shape in a side view having a pair of opposing plates 61a and 61b in each of which an opening 58 is defined with the generally same shape and size as the head accessing opening 55. A part 61 adjacent to the opening 58 acts as a lid plate. Two raised members 59 inwardly project on plate 61a by bending a part of the plate inwardly.
The raised members 59 are adapted to be slidably fitted in the guide slot 57 of the case 51. However, since the shutter 53 is made of a metal plate and the raised members are short, it is hard for the raised members 59 to be resiliently deformed when the shutter is mounted to the case 51, fitting the raised members 59 in the guide slot 57. In order to facilitate fitting the raised members 59 into the slot 57, there is formed one or more thin portions 60 in the front edge of the case 51 through which the raised members 59 are passed by bending the thin portions 60.
In order to protect the floppy disc from deformation by an external force, the case 51 is made of hard plastic resin materials. Therefore, it is difficult to produce a large amount of bending to the thin portions 60 in order to pass the raised members 59 since the resiliency of the case 51 is insufficient. Accordingly, to elongate the raised member 59 makes it difficult to mount the shutter 53 to the case 51. To cut the raised member 59 short makes it easier to mount the shutter on the case 51 fitting the raised members 57 in the slot, however, the shortened raised members 59 are easily disengaged from the slot, thereby resulting in easy disengagement of the shutter from the case 51. As mentioned above, control of the length of the raised members 57 must be severe.